Lecture 14 - Moulting animals Flashcards
Ecydsozoa
Moulting animals, descending from distant ancestors: Trilobite and Marella
Strengths and weaknesses of moulting
Allows damaged tissue and missing limbs to be regenerated or substantially reformed
The exoskeleton of arthropods cannot grow without moulting, leaving the animal vulnerable. An arthropod will moult several times during its life and is vulnerable for a period of time every time
Nematodes: what are they, what are their key features, how many species are there, and where can you find them?
Longitudinal organisms with collagen that absorbs oxygen. Lack of circular muscles causes whip-like movement
- Bilaterally symmetrical and triploblastic.
- Cylindrical in shape.
- Tissue-level organization.
- Cavity or Pseudocoelom.
- Alimentary canal is distinct
- Often parasitic
30,000 discovered but possibly more
Found everywhere: in/on organisms, water, water film, mud (one square meter is enough), soil (1 acre contains billions of nematodes), etc
Alimentary canal
The whole passage along which food passes through the body from mouth to anus during digestion.
Opisthosoma
The abdomen in spiders, contains the guts, heart, reproductive organs, and silk glands
Arthropods: what are they, what are their key features, how many species are there, and where can you find them?
Bilaterally symmetrical organisms with segments and jointed appendages usually with a chitin exoskeleton for protection and compound eyes
- Largest phyla
- Solid muscle anchor points
- Each segment has a pair of appendages
- Various forms of appendage (antennae, mouthparts, legs and more legs)
- Open circulatory system
- Have hemolymph instead of blood
- May have malpighian tubule
- May have mandibles (strong jaws)
Over one million discovered but up to ten million may exist
Everywhere.
Chelicerates: what are they, what are their key features, how many species are there, and where can you find them?
Two body segments: cephalothorax and abdomen without antennae but have six pairs of modified appendages
- Six appendages: four legs, chelicerae, pedipalps
- Chelicerae: modified appendages (pincers/fangs) * Pedipalps: small appendages leg/antennae-like that may be used for webs, feeding, sensing
- Absence of mandible and antenna
120,000 species: Pycnogonida (sea spiders), Merostomata (Xiphosurida (horseshoe crabs)), Arachnida (Araneae (spiders), Scorpiones (scorpions), Opiliones (harvestmen), Acari (ticks and mites)), etc
Largely terrestrial arthropods, living beneath stones and logs, in leaf mould, and in vegetation, but there are some aquatic mites that live in fresh water and in the sea.
Pycnogonida: what are they, what are their key features, how many species are there, and where can you find them?
“Sea spiders” that have an almost disappeared abdomen while the legs are long and clawed
- Larvae are not planktonic, so disperse slowly
- Carnivorous grazers – no digestive system
- Large surface area – absorb oxygen
- Males carry eggs and even larvae – close external fertilization
> 1,300 species
Found particularly in polar seas
Xiphosurida: what are they, what are their key features, how many species are there, and where can you find them?
An order of the Arthropoda phylum that, like chelicerates, has a body divided into two main subdivisions, the prosoma (head) and opisthosoma
- living fossils: existed nearly unchanged for at least 445 million years (before dinosaurs existed)
- Called horseshoe crab but closer to spider
- Long tail (telson) used to flip the organism
- Almost hunted to extinction until the hunting ban in 1970
Only 3 genera (4 species)
Found particularly in polar seas
Arachnids: what are they, what are their key features, how many species are there, and where can you find them?
A class of joint-legged invertebrates that contain six pairs of appendages: four pairs of legs, chelicerae, and pedipalps
- Cephalothorax (front) and abdomen (behind)
- Sexual dimorphism (female is larger)
- Zig-zag web structure (stabilimentum – unknown
function(s) - All spiders except one
species are carnivores
100,000 species
Spiders, scorpions, whip scorpions, mites,
Opiliones (harvestmen), Argiope spider (Spain)
Opiliones: what are they, what are their key features, how many species are there, and where can you find them?
The ‘weird’ spiders that do not produce silk, have a single body with an externally segmented abdomen
- Omnivores
- Penetrative sex
About 6500 species
Can be found in leaf litter, among foliage and in the grass in a wide variety of habitats.
Acari: what are they, what are their key features, how many species are there, and where can you find them?
Mites and ticks that have a single body part (the idiosoma) with four pairs of legs, chelicerae, and pedipalps
- Live in hair
- Absence of wings and antennae
- 0.1mm - 6mm size range
45,000+ species
Practically anywhere: hot springs, caves, harsh deserts, and tundras
Acari: what are they, what are their key features, and what animals?
Arthropods that have mandibles near their mouths
Include insects, crustaceans, and myriapods
Myriapods: what are they, what are their key features, how many species are there, and where can you find them?
Multilegged arthropods that have mandibles and respiratory exchange through a tracheal system
- Two body sections (head and trunk)
- One pair of antennae on the head
- Simple eyes
- Mandibles (lower jaw) and maxillae (upper jaw)
Nearly 13,000 species
Myriapods are most abundant and diverse in tropical and temperate forests
Diplopoda: what are they, what are their key features, how many species are there, and where can you find them?
Class of myriapod that contains two pairs of legs per segment (millipedes).
- Oldest known terrestrial animals
- Decomposers (especially deciduous forests)
- Monophyletic
- Trachaea and mandibles – like insects
- Thorax: four segments, each with 1 pair of legs, used in mating
- In some species, males brood eggs
Around 12,000 species
Mainly found in the soil, under rocks, or under the bark of trees
Chilopods: what are they, what are their key features, how many species are there, and where can you find them?
Class of Myriapod that contains one pair of legs per segment and may go up to 177 segments.
- Up to 177 segments, 1 pair of legs per segment
- Mainly carnivorous
- Trachaea and mandibles – like insects
- First pair of legs modified to be venomous fangs
- Some species are viviparous, most oviparous
- Male makes spermatophore out of silk, female picks it up
20 families, more than 3000 species
Found under rocks, logs or the bark of trees or in soil or leaf litter
Monophyletic
A group of organisms descended from a common evolutionary ancestor or ancestral group, especially one not shared with any other group.
Polyphyletic
A group of organisms derived from more than one common evolutionary ancestor or ancestral group and therefore not suitable for placing in the same taxon.
Paraphyletic
A group of organisms descended from a common evolutionary ancestor or ancestral group, but not including all the descendant groups
Viviparous
Producing live young instead of producing eggs to hatch
Crustaceans: what are they, what are their key features, how many species are there, and where can you find them?
A sub-phylum of arthropods having an exoskeleton of chitin or chitin and a compound of calcium
- Mainly aquatic organisms
- A few terrestrial forms (isopods, crabs)
- Have two pairs of antennae
- All except isopods require water for reproduction
- Most common examples (eg Decapoda) are orders
More than 67,000 species
Primarily aquatic – found in every marine and freshwater
environment
Crustaceans: what are they, what are their key features, how many species are there, and where can you find them?
A crustacean with an external shell, which attaches itself permanently to a surface and feeds by filtering particles from the water using modified feathery legs
- Largest penis length (proportionally)
- Hermaphroditic
- Extends and fertilises nearby barnacles
- Loved by Charles Darwin
Around 1,400 species species
Areas with lots of activity (underwater volcanos and intertidal zones) residing on sturdy objects (rocks, pilings, and buoys), and sturdy moving objects (boats, ship hulls, and whales)
Insects: what are they, what are their key features, how many species are there, and where can you find them?
Arthropods with three pairs of legs, one or two pairs of wings, and a pair of antennae (hexapods)
- Most successful class of animals: stable in virtually every ecosystem (only one major
lineage has gone extinct) - No insects live their whole life in seawater. Why?
- First animals to have powered flight, appeared at the same time as arboreal plants
More than one million species
Everywhere.
Are crustaceans mono, poly, or paraphyletic to insects
Paraphyletic on both sides
Hemimetabulous: what are they and what are their key features?
Insects having no pupal stage in the transition from larva to adult, continuous gradual growth
- Involves rapid changes within an organism (aquatic to aerial lifestyle)
- Moults
Holometabolous: what are they and what are their key features?
Insects with a pupal stage in the transition from larva to adult, with a complete metamorphosis occurring in the pupa
- Fly pupa’s most extreme transformation
- Other species show adult form also developing
- ‘Holometabola’
Coleoptera: what are they, what are their key features, how many species are there, and where can you find them?
“Sheath wings”: an order of insects that comprises all the beetles (including weevils),
- The largest order of animals on the earth
- Forewing hardened into elytron (chitin wingcase)
- Earliest beetles were detritivores/coprophages
- Beetle herbivory grows over time
- Larval stage enables exploitation of different niches
Around 300,000 - 400,000 species
Found in almost every imaginable terrestrial or aquatic habitat but many more species are found in tropical countries
Odonata: what are they, what are their key features, how many species are there, and where can you find them?
Dragonflies/damselflies: an order of insects that have long, slender bodies, aquatic larvae, two pairs of membranous wings, and large compound eyes
- Large heads
- Hair-like antennae
- Six legs
- Abdomen can have ten segments
- Dragonflies - perpendicular wings and big eyes
- Damselflies - parallel wings and bulbous eyes
- Mate guarding occurs (preventing female remating)
Around 5,900 species
Found near fresh water such as riverbanks, canals, ditches, ponds and lakes
Coprophages
Consume fecal matter
